Show all posts by user
General discussions. For specific printers / electronics / fabrication methods / softwares, please see other sections.
New England meeting, sometime in the next couple months? - 15 years ago
Greetings all, It sounds like there may be interest in holding another New England area meeting in the next couple months. (And maybe even increase the frequency to ~quarterly?) Topic focus TBD; feel free to chime in with your ideas. I was thinking about an extruder-building party; any interest? Anybody in the area reading this who isn't yet part of our google group, feel free to emailby Larry_Pfeffer - Massachusetts, Boston RepRap User Group
Re: Questions on driving DC motors with Arduino using PWM - 15 years ago
Geert, If you're regulating down for the cpu supply, there's really no reason not to try a diode upstream, to keep the capacitor. But one thing you might think about is to apply brute force instead of finesse. Getting a higher current supply might handle multiple motors better. Maybe going up to C cells, or a wall-wart supply. Does an A2D conversion on the Arduino really take 100 microsecby Larry_Pfeffer - Controllers
Re: Questions on driving DC motors with Arduino using PWM - 15 years ago
Geert, I was thinking about caps/decoupling for the CPU, rather than for the motors. Most CPUs are fussy about voltage, so a 1000 uFd cap won't hold the voltage within spec for very long. IHowever, it's still likely to work provided the short causes an interrupt, and your ISR is coded reasonably tightly. -- Larryby Larry_Pfeffer - Controllers
Re: Questions on driving DC motors with Arduino using PWM - 15 years ago
Geert, et al, Low-side current monitoring is easier, but won't catch all shorts. High-side is trickier, dealing with a small delta on a large common voltage. You might see if there's a "current monitor" IC that's simple/cheap enough to try. Allegro makes some, and likely others. Adding decoupling on the CPU supply (or beefing it up), may give the CPU enough time to disable the PWM channel(s)by Larry_Pfeffer - Controllers
Re: material conflustration -- different plastics - 15 years ago
Greetings all, I recall hearing that only some plastics contain plasticizers, usually brittle plastics. I suspect that HDPE doesn't contain plasticizers, but ABS may well, to address the rather brittle nature of styrene. -- Larryby Larry_Pfeffer - Plastic Extruder Working Group
Re: Foolproof extruder? - 15 years ago
Nophead, et al, Your comments about the thermal gradient and thermal impedance lead me to wonder if it's possible (and desirable) to shape the gradient to go from unmelted to freely flowing plastic in as short a space as possible. That is, confine the "hot zone" by reducing the area of metal conducting heat up (towards the PTFE) by thinning the outer diameter of the barrel down. At the pressurby Larry_Pfeffer - Mechanics
Re: easiest/ cheapest build - 15 years ago
Ant/Tony, et al, Can you give some detail on your linear encoders? They sound good -- but perhaps too good to be true. (I'd be happy to learn otherwise.) Small DC motors are widely available; in my experience, matching gearboxes (of sufficient ratio) are harder to find. Again, I'm interested in learning about your approach. -- Larryby Larry_Pfeffer - General
Re: Questions on driving DC motors with Arduino using PWM - 15 years ago
Geert, et al, I'm not familiar with the FT motors, but I suspect they're geared with a fairly high ratio -- and thus have substantial friction, even without being coupled to a load (which usually adds more friction.) Even with perfect electronics, the friction will still eat much of your torque, ~ 40%! Better torque estimation (e.g. by current measurement) might help, especially if used to modby Larry_Pfeffer - Controllers
Re: How to get extrusions to stick well? - 15 years ago
degroof Wrote: ------------------------------------------------------- > "Can you think of anything that's about 1' square, > 1/4" thick, porous, rigid and reasonably > heat-resistant?" Gypsum-board (AKA sheet-rock) might work, especially if the paper surface was roughed up or peeled off. Cement board, used as an underlayer below tile in shower stalls (at least in the US), might workby Larry_Pfeffer - Mechanics
G_Code and/or alternatives -- my opinions - 15 years ago
Greetings all, Text below is my opinion; feel free to agree, disagree, comment, or ignore: I think going to G-code as an intermediate representation for "operations a darwin/repstrap should do" is an excellent idea! In fact, skeinforge and the g-code (subset) interpreter for arduino are (together) a *major* reason I got off the fence and started restrapping. Whether additive or subtractive,by Larry_Pfeffer - RepRap Host
Humor: another reason to add subtractive machining -- Pumpkin carving! - 15 years ago
Greetings all, Here's a link (found via slashdot.org) on a novel use for CNC "machining" -- carving realistic faces onto pumpkins: Check it out (screenshots, still photos, no video of the process, alas.) I'm impressed with how realistic this looks! This makes me really wish I had my repstrap machine farther along. Maybe next year.... -- Larryby Larry_Pfeffer - General
Gerber viewers (in Python and otherwise) - 15 years ago
Greetings Khiraly et al, I found a page on a LINUX Gerber file viewer called gerbv: though I haven't yet tried it. (Note: Gerber format isn't the same thing as Gcode.) This page lists two other utilities written in python: >gerber2pdf. A Python script that converts a gerber file 2 pdf. > Seems quite advanced. >GerbMerge is also a panelizer, but written in Python. One of theseby Larry_Pfeffer - RepRap Host
Altetrnative material for kit mechanical parts - 15 years ago
Forrest Higgs Wrote: > So is there a better material that we should think > about using? I'm milling stuff out of HDPE and it > seems to be pretty robust. Greetins all, It costs more, but polycarbonate (e.g. Lexan) is *very* tough/durable and mills OK. (The chips sometimes stay attached, and need to be trimmed.) Cost might be offset by using thinner material, since Lex is so strongby Larry_Pfeffer - General
Re: mosfets instead of transistors - 15 years ago
Some things to remember about power MOSFETs: They're considerably more static sensitive than bipolar transistors. (An anti-static bag + aligator clip to ground is a cheap/effective anti-static mat -- very handy during handling/soldering/testing.) A power MOSFET's gate looks like a (non-trivial) capacitor; and can load (or overload) the driving stage while the cap is charging/discharging. (by Larry_Pfeffer - Controllers
Re: Connecting EMC to an existing mill - 15 years ago
Leav, et al, I just googled: EMC stepper and found a bunch of useful links, including this thread: Looks like a good old parallel port is still supported and common, but that's not the only way to go. Check the current rating on the steppers on your mini mill and lathe -- that'll let you determine whether the rrrf.org stepper drivers can drive them fully -- or whether you'll need hby Larry_Pfeffer - General
Re: Connecting EMC to an existing mill -- Parallel port, I *think* - 15 years ago
Leav, et al, It's been awhile since I looked at this, but I think the most common way for an EMC system to connect to stepper motors was via a parallel port -- using two bits per motor, to drive step and direction on various stepper driver modues, much like the reprap arduino uses to drive the stepper controllers. If that's so (don't take my word/memory -- check the EMC site), you'd need a paraby Larry_Pfeffer - General
Re: mcwire cartbot....drilling holes - 16 years ago
Robert, I've never seen a McWire in person, so I don't know exactly what you mean by "locate the same center twice" -- so plkease bear with me if the following is wildly irrelevant. It sounds like you need (among other things) to make accurate lines on the pipe, parallel to the axis. (I'd suggest making only one line , and drilling straight through the far wall, rather than marking/drillingby Larry_Pfeffer - Reprappers
Re: mcwire cartbot....drilling holes - 16 years ago
Robert, et al, First off, centerpunching the desired starting point should help prevent the drill bit from skating off. I find that a pilot hole around 1/8" (or 3 mm) is a good trade-off between drill sturdiness and amount of metal removed. They're also cheap if you bust one.... Having some sort of guide to keep the drill perpendicular to the pipe is key. To keep the pipe from rolling, suppoby Larry_Pfeffer - Reprappers
Re: smd -> DIP (or SIP) - 16 years ago
Greetings Niel, at al, These already exist. Here are two manufactcurers (there may well be more): Aries "correct a chip: : "surfboards" I don't know if either sells in small quantities. One still has to solder the smd part onto the adaptor, but these at least isolate that to a small board that could be soldered separately. HTH, Larryby Larry_Pfeffer - Let's design something! (I've got an idea ...)
Re: RepRap near future - 16 years ago
Greetings all, I'm not convinced that a standard release is the best thing for all participants. "One size fits all" often means a poor fit for many. We each bring different skills to the project, have different interests and differing budgets. An alternative might be an "Annotated Taxonomy of Reprap/Repstrap designs." A part of the Wiki that explains the alternatives and the constraintsby Larry_Pfeffer - General
Units correction (Nit-picky, I know) - 16 years ago
Forrest Higgs Wrote: ------------------------------------------------------- > A slug is a unit of mass in the US common system > of measurements. Most people think that both kg's > and pounds measure the same thing. All true. > Thus the slug > in the US common system is the equivalent of the > Newton in SI. Not quite. Both slugs and Kg are mass measures; both pounds andby Larry_Pfeffer - General
"Interesting" units and their application - 16 years ago
Ru Wrote: ------------------------------------------------------- > Ooh, thats a dead useful page. Well found. > > I'd never even heard of the measurement of 'slug > feet' before. Slug-feet my be an archaic measure, but it's quite useful for quantifying sliminess -- applicable to lawyers, hedge-fund managers, and politicians. ;-) For such applications, the prefixes mega, giga orby Larry_Pfeffer - General
Re: cnc for reprap: Probably doable, but the KX3 is an expensive way to go. - 16 years ago
leggazoid Wrote: ------------------------------------------------------- > Would either of these mills work for a reprap > machine? Based on the review, the KX3 looks to me like a good basis for repStrapping, although IMHO, it's rather expensive overkill -- unless you wanted an off-the-shelf CNC machine, anyhow. -- Not that that'd be a bad thing at all! You'd also have to be up for doiby Larry_Pfeffer - Reprappers
Re: Question about plastics - 16 years ago
Pizentios, et al, With the current heated extruder, reprap is basically constrained to using thermoplastic, rather than thermoset polymers. Although it may not be as satisfying as making plastic from raw materials, but recycling existing plastics has been discussed on these forums, and people are making some progress. (You might try searching the forums for the terms granule and/or recycling.by Larry_Pfeffer - General
Re: "Machine goes to workpiece" - 16 years ago
Victor, Thanks for posting that -- interesting. That machine reminds me somewhat of the hexapod router -- in that the tool travels to the material, instead of the reverse. If the registration issues could be worked out, this general approach might let a small machine create a larger child, that could (in turn) build still a larger child.... up to pyramid-extruding machine! Imagine the rollby Larry_Pfeffer - Mechanics
Alternative Elect. Insulator/Thermal *conductor* under Nichrome, Mica. - 16 years ago
Joshua, et al, I wish I'd pondered a bit more before my msg (above) re anodizing. Although anodizing can probably be made to work, here's another idea that (if it works) doesn't require an Aluminum barrel, or mucking about with nasty chemicals. A thin MICA insulator between the nichrome and the barrel might do the trick, if we can get mica thin enough not to crack, when bent to the barrel's oby Larry_Pfeffer - Mechanics
Feasibility of Anodizing under the nichrome wire? - 16 years ago
Joshua Merchant Wrote: ------------------------------------------------------- > Wait a minute, I'm using an aluminum barrel... why > can't we (I! I mean I, really!) just anodize it? > says > anodising can be used to increase the thickness of > the natural oxide layer (which in aluminum is > normally very thin). Joshua, Apparently anodizing is doable in a home-shop environby Larry_Pfeffer - Mechanics
Re: Laser Cut Parts (Bits from Bytes) Material suggestion -- Polycarbonate? - 16 years ago
Greetings all, Would Polycarbonate (e.g. Lexan) work for laser cutting? It's available in black as well as clear, and is *much* more rugged than other plastics. It (Lex) costs a little more than acrylic, but is very tough stuff, and very difficult to break by tightening fasteners. My impression is that the cutting and shipping dominate the costs, so using a more durable material might be anby Larry_Pfeffer - Mechanics
Re: Repstrap project - 16 years ago
Corwin, et al, FYI, a quick google search turned up at least one supplier for this stepper driver: To avoid the need to replace, a generous heatsink would help, as will a fan and thermal compound. -- Larryby Larry_Pfeffer - Reprappers
Idea re the Wanted, for Sale forums: Combine, add "for Swap" - 16 years ago
Greetings forum Admins et al, Given the minimum purchase requirements for some reprap and repstrap materials, I would like to explore the idea of swapping among reprappers, as an alternative to buying/selling for cash. To me, this seems more in the cooperative spirit, whatever economists say about barter.... It might also make it a bit easier for people to experiment with reprap/repStrap desiby Larry_Pfeffer - Administration, Announcements, Policy